In this proposal, Nanotherapeutics proposes to investigate inhaled dry-powder formulations of two aminoglycosides, streptomycin and gentamicin, for post-exposure treatment of aerosol exposure of the Category A bioterrorism agents pneumonic Yersina pestis (plague) and Francisella tularensis (tularemia). It is proposed that inhaled formulations of aminoglycosides, currently the first-line therapy for pneumonic plague and tularemia, will produce high local drug levels quickly (seconds) in the lung to treat an aerosol exposure, compared to injection which requires a health-care worker and may take hours to implement. In the event of an accidental or deliberate aerosol exposure, streptomycin and gentamicin are the recommended drugs for postexposure prophylaxis and treatment for the Category A agents Yersina pestis (plague) and Francisella tularensis (tularemia), as well as the Category B agent Brucella. Also, because of the danger of aerosolized distribution of bioterrorism agents, such as the incidences with anthrax in the US Post Offices post-9/11, immediate post-exposure prophylaxis using single-dose disposible inhalers with adequate shelf-life stability would be beneficial. Compared to early-stage discovery efforts which may take years to produce a viable product, streptomycin and gentamicin are FDA-approved for injection, and nebulized gentamicin has been used clinically to treat Pseudomonas respiratory infections for many years. The main objectives of this Project is to (1) compare steptomycin and gentamicin particle formulations measuring the particle size, aerosol properties, and cytotoxicity in pulmonary cell cultures in vitro and (2) compare inhaled administration in vivo in rodents at different doses to identify pulmonary absorption and residence time, as well as tissue-specific toxicity. Secondary objectives of this project are to compare different dosing regimens, including (3) dosing frequency and (4) time lag to first dose, to identify the best post-exposure treatment following a pneumonic plague or tularemia nasal challenge in mice (BSL-3). The goal at the end of the project is to identify a safe and efficacious aminoglycoside inhaled treatment regimen for further clinical testing. Specifically, we will: Specific Aim 1: Evaluate different aminoglycoside particle formulations in vitro for efficiency in producing 1 to 5 micron particles and assess aerosol properties, release-rate, and shelf-life stability. Specific Aim 2: Evaluate the in vitro toxicology / susceptibility and in vivo pharmacokinetics in rats of different particle formulations to assess the safety / efficacy and support drug formulation selection and dose for efficacy studies in mice. Specific Aim 3: Establish the efficacy of selected inhaled aminoglycoside formulation in post-exposure prophylaxis after a nasal challenge in mice.